Stenhelmoides grandis

Stenhelmoides grandis

DIAGNOSIS.—Differs from all known species of Stenhelmoides in pattern of the pronotal plastron (Figure 98) and male genitalia (Figures 151, 152). Although the dark medial pronotal area without plastron is similar in shape to that of S. guyanensis, the discal area of S. grandis is densely granulate (Figure 98) and that of S. guyanensis is without granules (Figure 95).

HOLOTYPE MALE.—Body Form and Size: Elongate, parallel sided (Figures 127, 129), moderately convex dorsally (Figure 128). Length, 4.40 mm; width, 1.70 mm.

Color: Dorsal surface dark reddish brown overlaid with gray plastron except an elongate, sinuous area on midline of pronotum, the scutellum, and a narrow area along sutural margins of elytra without plastron. In addition, dark gray-brown rounded macula present on each side at about midlength of pronotum. Each elytron with the following elongate maculae: one on base at midwidth, about 3 times length of scutellum; one laterally and one subsuturally at midlength; and one laterally and one subsuturally just before apex. Clypeus, labrum, antennae, and palpi reddish. Gena with gray plastron setae (Figures 135, 136). Legs reddish except profemur and mesofemur each with black to dark gray-brown macula at midlength; macula more obvious on side normally lying against sterna. Venter dark reddish brown to black but overlaid with gray plastron. Abdominal sterna with wide area of light gray plastron laterally that contrasts abruptly with darker gray middle area.

Head: Width between antennal acetabula, 0.10 mm (Figures 130, 132). Frons gray. Granules pointed (Figure 131), less coarse than facets of eyes. Clypeus finely granulate. Labrum with a transverse row of hair-like setae near midlength. First antennal segment subequal to combined lengths of segments 2–4.

Thorax: Pronotum, 1.40 mm long, 1.47 mm wide at basal third; with gray plastron except median microreticulate area (Figure 133); extremely shallow median longitudinal line extending from near base to midlength. Pronotal granules flat (Figures 133, 134), slightly smaller than facets of eyes, separated by 1 to 2 times the diameter of a granule; slightly more widely spaced apically and basally; smaller and denser in median reddish area; each granule with short basal seta; setae of all granules directed toward median basal fifth of pronotum. Hypomeron with scale-like plastron setae (Figures 146, 147). Elytra, 3.01 mm long, 1.43 mm wide (slightly past midlength). Each elytron with 6 distinct longitudinal bands of granules, 5 discal bands more evident than lateral band; granules (Figure 137) similar to those on pronotum; each granule with a basal seta directed obliquely toward midline; reddish sutural margin finely punctate and indistinctly microreticulate. Epipleuron with scale-like plastron setae and granulate (Figures 149, 150). Scutellum subtriangular, without plastron (Figures 137, 138). Prosternum 0.85 mm long; apicomedial area reddish and not granulate, remainder with gray plastron; with large, flat, round granules; granules (Figure 144) separated by ½ to 1 times granule diameter in midline, only slightly sparser laterally; prosternal disc slightly angulate at border of reddish area. Prosternal process 0.35 mm long and 0.39 mm wide; apical half deflexed slightly; apex broadly V-shaped. Mesosternum with deep fovea for reception of apex of prosternal process. Metasternum with gray plastron on disc; disc very shallowly depressed and granules similar in size but denser than those of prosternal disc; midline with deep sulcus; lateral angles of intercoxal process not strongly elevated; metasternal disc and intercoxal process of abdomen on same plane. Granules on intercoxal process between metacoxae coarse and dense. All tibiae with a prominent row of dense, subsinuate, stout, scraping setae on inner margin. Tibial cleaning fringes as follows: protibia (Figures 142, 143)—short, very narrow band occupying middle third of anterior surface; mesotibia and metatibia—distal of posterior surface. Mesotibial cleaning fringe (Figure 145) bordered apicolaterally by 10 stout, smoothing setae; metatibial cleaning fringe (Figure 148) bordered apicolaterally by 8 stout smoothing setae. Anterior surface of profemur with only 2 long, slender, golden, hair-like setae at midlength (Figure 141). Posterior surface of mesofemur with distinct row of long, hair-like setae at midlength. Protarsal, mesotarsal, and metatarsal segments with short sparse setae ventrally; tarsal segments 1–4 of protarsus (Figures 139, 140) and mesotarsus with moderately dense hair-like setae, setae almost as long as width of second tarsal segment.

Abdomen: Granules on intercoxal process slightly larger and slightly more dense than granules on metasternal disc, becoming sparser and smaller laterally and apically; last sternum with minute granules. Sternum 5 evenly rounded; without depression or distinctive apical setae.

Male Genitalia: As illustrated (Figures 151, 152).

FEMALE GENITALIA.—As illustrated (Figure 153).

VARIATIONS.—This species varies primarily in its color. On several specimens the maculae on the dorsum are plainly evident and on others they are indistinct. The black macula described for the profemora and mesofemora of the holotype is indistinct on several specimens on the ventral surface but is distinct on the upper surface, which lies against the sterna.

Females are without the moderately dense hair-like setae on segments 1–4 of the protarsus and mesotarsus.

TYPE DATA.—Holotype (male) and Allotype: VENEZUELA: TERRITORIO FEDERAL AMAZONAS: Cerro de la Neblina, Basecamp, 140 m, 0°50′N, 66°10′W, 20 Feb 1985, P.J. and P.M. Spangler, R.A. Faitoute, W.E. Steiner; deposited in National Museum of Natural History, Smithsonian Institution.

Paratypes: BRAZIL: AMAZONAS: Manaus, 11 Sep 1937, 1, 1 (BMNH). FRENCH GUIANA: Rivière Lunier, F. Geay, 1899, 1 (MNHN). VENEZUELA: BOLIVAR: El Dorado (65 km S), 5 Nov 1982, R.F. Denno, 1 (coated for scanning electron microscopy) (USNM); Las Cocuizas (5 km N), 2 Nov 1982, John L. Hellman, 1 (USNM). TERRITORIO FEDERAL AMAZONAS: Same data as holotype, 2 one deposited in Universidad Central de Venezuela at Maracay.

DISTRIBUTION.—Presently known only from Brazil, French Guiana, and Venezuela (Figure 154).

ETYMOLOGY.—From the Latin grandis (large), in reference to its large size.

HABITAT.—The holotype and 3 additional specimens were collected from the rocky shallows (Figure 155) of the Río Baria at Cerro de la Neblina, Venezuela; altitude, 140 m. At the collection site, the Río Baria was an unshaded blackwater stream about 25 to 35 meters wide and about 0.5 to 1.0 meter deep (during a period of low water). The stream had a sand, gravel, and rocky substrate and was subjected to flash flooding; the elmid fauna was diverse and abundant at the site. Colorimetric water chemistry analyses at the base camp, where the holotype et al. were collected, was as follows: pH, 4; hardness, 0; oxygen, 12 ppm. The water temperature was 27°C at the time the analyses were made.

Other aquatic beetle genera collected with Stenhelmoides from the same riffle area in the Río Baria are: Dytiscidae: Bidessodes, Hydrodessus, Hypodessus, Laccodytes, Microdessus. Elmidae: Cylloepus, Gyrelmis, Heterelmis, Hexacylloepus, Hintonelmis, Macrelmis, Microcylloepus, Neoelmis, Pagelmis, Stegoelmis, Tyletelmis, Xenelmis. Gyrinidae: Gyretes.